There is well known a control apparatus for a vehicular drive system including a differential portion having a first element connected to an engine, a second element connected to a first electric motor and a third element connected to a power transmitting member and operable to distribute an output of the engine to the first electric motor and the power transmitting member, and a transmission portion provided in a power transmitting path between the differential portion and a drive wheel.
Patent Document 1 discloses an example of a control apparatus for such a vehicular drive system wherein the differential mechanism is constituted by a planetary gear set, and the differential portion includes a second electric motor operatively connected to the power transmitting member, while the transmission portion is constituted by a step-variable automatic transmission. The drive system has an overall speed ration defined by a gear ratio of the differential portion functioning as a continuously-variable transmission, and a gear (speed ratio) of each gear position (speed position) of the transmission portion.    Patent Document 1: JP-2006-118667 A    Patent Document 2; JP-2003-199212 A    Patent Document 3: JP-2005-313865 A    Patent Document 4: JP-2005-318780 A